The present invention relates generally to an aerodynamic shape which provides improved lift characteristics, and in particular, to the use of such an aerodynamic shape in conjunction with an air damper to achieve improved operational characteristics.
In general, air dampers commonly referred to as backdraft dampers are used to permit the flow of air through a ventilation system in one direction only, to ventilate an area of a structure while preventing the entry of air from the exterior of the structure being ventilated during normal operating conditions. In the development of such backdraft dampers, workers skilled in the art have long sought to develop a device having blades which are easily moved from their normally closed position wherein the damper blades combine to form an effective air seal, to an open position which permits the unimpeded flow of air through the device when ventilation is necessary. The development of such a backdraft damper would permit vented air to pass from the interior of a building to the exterior environment while precluding wind, backdraft, rain, dust, smoke or obnoxious fumes from entering the interior of the building through the damper.
To achieve the foregoing results, a variety of backdraft dampers have been designed which primarily operate in response to the differential pressure developed across the damper when ventilation is to be performed. During normal operating conditions, the blades of such dampers combine to develop an efficient seal which is capable of preventing the passage or leakage of air, in the wrong direction, from between the closed blades of the damper. When ventilation is needed, the blades of such dampers readily open in a manner which reduces resistance to the flow of air through the damper, to maximize its ventilating capabilities. Two such backdraft dampers are described in my prior U.S. Pats. Nos. 3,908,529 and 3,381,601, for example. In addition, reference is made to U.S. Pats. Nos. 3,833,989; 3,327,764; 3,581,650 and 3,605,603, which show other constructions which may be used to produce a series of blades which are pivoted for rotation within a frame to develop a backdraft damper having adequate operational characteristics.
Although the foregoing devices serve to achieve the required operational characteristics of a backdraft damper, it has been found that such devices are capable of still further improvement. For example, to assure that the damper blades operate properly and do not flex during operation of the damper, the blades of each of the foregoing devices must generally be formed of relatively thick or heavy gauge materials. This is particularly so as the size of the damper is increased, necessitating the use of still larger blades. The weight of such damper blades tends to compromise the ability of the damper blades to quickly and fully open, accordingly limiting the ability of the backdraft damper to ventilate an area by limiting the flow of air through the damper.
In an effort to overcome this, attempts have been made to develop damper blades having improved aerodynamic characteristics which assist in lifting the blades as air passes through the damper. One example of such a damper construction may be found in my prior U.S. Pat. No. 3,204,548. Such aerodynamically shaped blades tend to compensate for the weight of the materials which are used to construct the damper blades, permitting dampers constructed of such materials to ventilate increased volumes of air from a structure without sacrificing damper integrity. However, again, such damper constructions are capable of still further improvement. In particular, it is desirable to develop a damper blade having still further improved lift capabilities, to further improve the efficiency of the damper. Further in this regard, since the flow of air through such dampers often occurs at relatively low velocities, the aerodynamic shape developed should be capable of providing such improved lift characteristics, even at low speeds, to further improve the efficiency and range of the damper. Moreover, it is desirable to develop a damper construction having increased simplicity in construction, to decrease the cost of manufacturing such dampers.